Process for effecting double conversion between two solutions of ionogenic substances by using ion exchangers



June 19. 1956 w. HASSELDER 2,751,230

PROCESS FOR EFFECTING DOUBLE CONVERSION BETWEEN TWO SOLUTIONS OF IONOC-ENIC SUBSTANCES BY USING ION EXCHANGEIRS Filed Jan. 15, 1953 FIG. I

FIG. 2

WWW BY WGMJZ/FMW United States Patent PROCESS FOREFFECTINGDOUBLE CONVERSION BETWEEN TWO SOLUTIONS OF IONOGENIC SUBSTANCES BY USING ION EXCHANGERS Willem Hasselder, Geleen, Netherlands, assignor to Stamicarbon N. V., Heerlen, Netherlands ApplicationJanuary 15, 1953, Serial No. 331,473 Claims priority, application Netherlands January 19, 1952 7 Claims. (Cl. 23-90) The present invention relates to a process of converting substanceswhich are ionized in solution (i. e., bases, acids, salts) with the help of ion exchangers. and, more particularly, the invention pertains to a method of loading and regenerating, the ion exchanger used in this conversion process.

Field of invention.

It has previously been proposed to cause the conversion of two soluble salts, hereinafter broadly referred" to as BlAl and BzAz, with the help of ion exchangers, to-proceed in such a manner that two diiferent salts B1A2 and B2A1 are obtained according to the equation: 1) B1A1+B2A2 B1A2+B2Ai The I. E'., which is now charged with B2 ions, is subsequentlywashed with water andv thereafter regenerated by passing a solution of the salt BiAi over it. I The second phase of the conversion. process, the socalled' regeneration of the I. E., may be represented by the equation:

Byaddition of; thesEq-uations '2 and 3; supra, it will' be seen that a double conversion is obtained between the salts BiAi: andr'BzAz, as a'resultof which the salts BlA'al'ld BQAI are :formed; the L E. having only functioned'as'a'n ion carrier;

.The behavior ofthe'rl. E. with respectltothe 'Brions isdifierent from the IL. E. behavior with B2 ions, a'n'dfas will be appreciated'from the foregoing;particularlyfrom Equations hand-:3, it isa-assumed herein-thatthe' Bz'i'ons are more firmly bound-to 'the IJE; than the B1 ions.- As' a loading result, regeneration? oflthe I. E. is: more dilhcult' than the loading thereof.

-It will be appreciated from theforegoingi' that by" the term loading of the: I-. E., as used in: this specification and the appended claims-,isto be understoodz'that process inwhich the LE. containing. a particular ion: is contacted with. a solution containing another ionwhich it isdesired to substitute forthe ion'ot the I. E. aHd'WhlChIlSIHOITG' firmly bound. by, -the.:I. Etithan the one; whichthe'l. is to release;.-

The term;v regeneration, as used-in the' specification and claims, standsifor theproeess wherein the I. loaded with aparticulan ion. is:contained with a regenerating solution. containing. another ion which in all; or ini-pa-rt, oi the mixing ratioslinwhiclr the twoions may-besprese'nt sfdeiby sidein the solution, isless firmly bound by'the I. E. than the ion with which the I. E. is loaded.

Z,75l,280 Patented: June19, 1956 In effecting doubleconversions between solutions" of ionogenic substances B Ai and BzAz, the alternatingl'oading and regenerating steps are generally .c'a'rried out' in two sets of columns, arranged in series and filled with ion exchanger. With such an arrangement, one of the sets of columns is contacted witha BzAz solution and is; consequently, loaded, whereas the other set of columns. is subjected to a regenerating treatment by' supplying thereto a B1A1 solution.

The necessary alternating loading and regeneration of the ion exchanger is effected by periodically disconnecting the first column of one set and;'after washing the column to remove the solution leftin the-free spaces'between the particles of ion exchanger, connectingsame: to the discharge side ofthe other set of columns. 1

As a result of theproperty of the'l. E. whereby exchange, or replacement,- of the Bz'ion by the B1 ion ("regeneration) is attended with greater diificultythan the exchange .of the B1- ion with the B2 ion (loading), it has been found impossible, in-threi absence of specific treatme'nt of the starting or intermediate liquors, to discharge a virtually pure BiAz. solution from the'set of columns which is. loaded 'by supplying. thereto" a BzAz solution; and at the same time todischarge a-virtually pure BzAi solution fromthe second set of columns regenerated by means of a BIA],- solution. In other words; if. the operatingcon ditions selected are such that, asra result of therloading,a virtually pure BrAz solution isobtained, the regeneration operation with a BiAi. solution produces a BaAr solution containing-a .considerable amount of BiAr. Likewise, if the regeneration-iscarried out insucha way as to result in the formation of. avirtuallypure B2A1- solution, the loading operation produces a solution which contains, in addition tothe desired BrAz, an appreciable amount: of B2A2.

The quantitative separation of many substances met with in the form of mixed-solutions in double conversion proceduresparticularly simple substances such as KGl, is impossible most cases. .A portion of suchr substances can, of course,.-g,enerally:be recovered by crystallization or other conventional technique, but ultimately liquors are obtained which. cannot be. worked any further. Such liquors necessarily.represent losses-of desired substances.

It hasnow. beenfoundpossible with certaincritical and novel modificationsinthe procedures generally described above to-efiect idouble conversion between solutions of ionogenio substances. with. the help of an ion exchanger in such a way that the ditficulties noted abovecan be avoided with the result that when starting with solutions of B1A2 and B2A1, approximately' equivalent amounts of substantially pure BZAl anda-BrAz can be obtained in a convenientmanner. I

. Objects g, Y Accordingly, the principal object of the presentinvenztion: is-the provision of anovel improvement in effecting doubleconversion between solutions of ionogenic substances. 1 A- more specific 'object-of'theinvention is the provision of new procedures forloading and regenerating columns filled withflion eucharvgerfor the purpose of efiectin'g doubleconversions, said procedures being. free of the dis? advantages-noted above.

Otherobjectsinclude: Y (a) The provision of improved procedures for effecting doubleconversi'on' between two solutions of ionogenic'substances, herein= referred toasBrA-r and B2A2, using? columns filled with a suitable ion exchanger whereby asubstantially pure solution-of BaAr and substantially pure crystals of BiAz. can be simultaneously obtained in: ahigh- 1y convenient way. a

groups of columns containing ion exchanger and involving novel improvements in loading and regenerating the ion exchanger whereby the double conversion may be carried out in a more economical way.

Still further objects and the entire scope of applicability of the present invention will become apparent from the detailed description given hereinafter; it should be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.

Description Briefly stated, the objects outlined above are realized according to the present invention by a process involving the steps of providing a first group of columns connected together in series to be loaded and a second group of columns connected together in series to be regenerated, passing the loading solution through the first group of columns to load the ion exchanger therein, and withdrawing from the last column of this first group of columns a solution containing the product formed by the loading operation and the ionogenic substance of the loading solution, removing the product formed .by the loading operation from the withdrawn solution, returning the resulting liquor to an intermediate column in the group of columns being loaded, feeding the other solution of ionogenic substance through the second group of columns to be regenerated and withdrawing a substantially pure solution of the product formed in this regenerating operation from the last column in this second group of columns, disconnecting the first column in the group of columns being regenerated when said column is partially regenerated and connecting same as the last column in the group of columns being loaded, disconnecting the first column in the group of columns being loaded and connecting same as the last column in the group undergoing regeneration, and thereafter repeating the loading and regenerating operation through the new groups of columns and removing the product formed during the loading operation, the resulting liquor being returned to the column being loaded adjacent and subsequent to the intermediate column to which said liquor was previously returned.

- The success of the invention resides, at least to a substantial extent, in two features: (a) regenerating the columns only partially, rather than completely, as is customary, while obtaining a substantially pure solution of the product BZAI resulting from regeneration, i. e., substantially completely converting the regenerating agent to give a solution in which the molar ratio of and (b) in the loading phase, removing the desired conversion product B1A2 from the solution withdrawn from the last column in the group being loaded, as by cooling and crystallizing, and returning the resulting mother liquor to an intermediate column, e. g., the fourth column in a group of six columns.

in essence, the group of columns being loaded is itself divided into two groups, and the loading operation is effected by passing a solution of a loading agent (BzAz) successively through a first group of these columns and thereafter the solution discharged from the last column of this first group is passed through a second group of columns to be loaded. The solution discharged from the last column in this second group, which is rich in B1A2 and relatively poor in BzAz, is freed of most, or at least a substantial part, of the BiAz dissolved therein, in any conventional manner, e. g., by cooling and crystallizing the solution in auxiliary apparatus. The remaining mother liquor, which now contains more BzAz than BlA2, is continuouslyconcentrated by evaporation and subsequently is returned to the first column of the second group undergoing loading. Periodically the loading operation is stopped and the first column of the first group, which has been completely loaded in the meantime, is disconnected and cut out of the circuit, the first column of the second group is made the last of the first group and a new column, which has just been regenerated and Washed, is introduced at the end of the second group. Thereafter the loading operation is repeated.

In order that the invention may be more readily understood, the manner of carrying the invention into effect is hereinafter described with reference to the accompanying drawings in which:

Figure l is a flow diagram of the loading operation, and

Figure 2 is a flow diagram of the regeneration of the columns containing the ion exchanger.

In Figure l, C1, C2 Cm represent a first group of a limited number (m) of columns arranged in series; D1, D2 Dn represent a second group of a limited number (n) of columns arranged in series, and Cr and Ev represent, respectively, a crystallizer and evaporator arranged after the last column of the second group.

In Figure 2, E1, E2 Ep represent a series of a limited number (p) of columns to be regenerated.

Periodically the columns are disconnected, connected and switched over from one group to the other in such a way that:

Column E1 will come to function as Dn in the preceding period;

Column E2 will come to function as E1 in the preceding period;

Column Ep will come to function as Ep-l in the preceding period;

Column C1 will come to function as E in the preceding period;

Column Cz will come to function as C1 in the preceding period;

Column Cm will come to function as Cm-l in the preceding period;

Column D1 will come to function as Om in the preceding period;

Column D2 will come to function as D1 in the preceding period;

Column Dn will come to function as Dn-l in the preceding period.

During each period a BzAa solution is supplied to column Ci; successively the solution traverses the columns C and D, the ion exchanger in the columns taking up the B2 ion while releasing B1 ions.

From the column Cm a solution rich in BiAa is discharged. However, this solution is not pure, since it also contains some B2A2. In the auxiliary apparatus denoted by Cr, a large part of the dissolved 131A: is removed from this solution by cooling, crystallizing and separating the crystals from the solution. The remaining mother liquor is concentrated by evaporation in the auxiliary apparatus Ev and subsequently continuously returned to column D1.

The proper composition of the ion exchanger in the column D1, which is periodically switched over from the second group of columns to the first, the amount of the mother lye circulating in the second group of columns to be loaded after the separation of BiAz, as well as the total number of columns needed, will vary, and must be determined for each separate case by means of equilibrium measurements and solubility diagrams.

However, when working in the manner outlined above, it is always possible to produce an initial column in the first group, which at the end of each loading period is filled with an ion exchanger that has been converted completely into the (B21. E.) state. Furthermore, during this loading operation pure BiAz crystals can be obtained from the solutionv discharged from the last column of the second group. The mother liquor remaining after aveiiaso the B1A2 crystallizationmay then. be returned to the first column of the second group without losses. 8

It is to be noted'that since the regeneration phase .is conducted, according. to the present invention, in such a way as to produce a virtually pure BzAi solutionfrom' a BiAi solution, the column E1 which is disconnected from the series of columns E at the end of a regenerationperiod is never fully regenerated. That is to say, column E1 always contains a minor amount of (B21. E.) along with an excess amount of (BLI. E.).

It will, of course, be appreciated that the invention may be applied for double conversions brought about both with cation and anion. exchangers, and for the purpose of eiiecting double conversion of all substances to which double conversion by ion exchanger is applicable. The following example illustrates-.further the nature of the invention and the manner in which it may becarried into efiect- Example A double conversion was'ett'ected between a Ca(NO3-)-2 solution and aKCl solution. resulting in the production of KNO: crystals and a CaClz solution.

The cation exchanger used in this example was the normal commercial product Dowex 50 (-a sulfonated styrene). This ion exchanger has the property of more readily exchanging Ca ions than vice versa. Hence, the KCl solution functions as the BIAI solution (regenerating agent), and the CaNOs solution as the BzAa solution (loading agent)- i The loading operation was carried out in six columns arranged in series and dividedinto two groups of three columns each. For the regenerating operation a number of three columns arranged inseries was utilized.

Each column contained 100 liters of Dowex 50; the capacity of each column amounted to 218 grams equivalents of CaO, and the free space between the grains of cation exchanger amounted to 40 liters per column.

Per regeneration period 100 kg. of a 25% KCl solution was supplied to the first of the series of columns to be regenerated, while a total amount of 62 kg. of CaClz solution with a CaClz content of 15.6% and a KCl content of 0.2% was discharged from the last column after a first draw-oft of about 30 kg. of water, which had been left behind in the free spaces between the grains of Dowex 50 as a result of the washings between each regeneration and loading of the column.

The first column of the series of columns undergoing regeneration was 80% regenerated into the K ion loaded state. In the free spaces between the grains of Dowex 50, 48 kg. of a 25% KCl solution was left behind. This KCl solution was regained by washing, after which the column was added to the end of the set of columns to be loaded.

Per loading period, 81.8 kg. of a 60% Ca(NOa)2 solution (temperature 90 C.) was supplied to the first of the set of columns to be loaded. After a first drawofi of about 30 kg. of wash water, 55.5 kg. of a solution was discharged from the last column of the second group, said solution containing an average of 13.5% Ca(NOs)2, 38.7% KNOs and 47.8% H2O.

By cooling, crystallizing and centrifuging an amount of 17.6 kg. of KNOs crystals was obtained from the aforementioned solution of mixed salts obtained from the last column of the second group of columns being loaded. Twenty kg. of water was removed by evaporation from the mother liquor per period, the thus concentrated mother liquor being supplied to the first column of the second group. This quantity of mother liquor amounted to 18.4 kg. per period, with an average makeup of 40.8% Ca(NOs)z and 21.2% of KNOB.

The first column of the first group of columns being loaded, disconnected at the end of a loading period, was loaded for 100% with Ca ions. In the free space between the grains of Dowex 50, 58 kg. of a 60% Ca(NO3)2 loading solution, was left behind',lisonie heingreg'ained by washing before the column wasregenerated.

' Summary The present invention provides a new and highly ad'- vantageous process for carryingv out double conversion between twdionogenic'solutions, e. g'.,. the double conversiori between KCl' .and Ca(NO's)z to give KNO: and C3Cl2.

As will be appreciated, the process of theinvention otters the advantagesfof discharge 'fro'mion'exchangercontaining'columns of a substantially pure solution ofa compound containingtheaion removed from the indexchanger during regenerationf Atthe safnetime, the invention' provides,;duriiig the loading. operation, substa n-, tially pure crystals of a second'compouiidina way which eliminates. the necessity ,of attempting. separation from mother liquors which. cannot. be completely broken down into theirconstituents.

It will also be" appreciated, that, .duetothe new improved process described liere'in,f.it".is possible tocarry out double conversions ..particularly where relatively simple compounds are involved. in .a much. more; economical way'than hithertorpossible. I

Q Having described my invention what I claim is:- l. In effecting doubleconversion. between two solutionsof ionogenic substances by al'ternat'ely contacting columns filledwithion exchangenfirst with. one of said solutions to load the lion. exchanger and then 'withthe other 6r: said. solutions .to..regenerate. the-ion. exchanger j si'ng, a process involvingL-the steps-of providing a. first group of columnsconnected together inseriesto. be loaded and a second" group .ofacolumns connected together in series 'to be regenerated, passing the loading solution through the first group of columns to load the ion exchanger therein and withdrawing from the last column of this group of columns a solution containing the product formed by the loading operation and the ionogenic substance of the loading solution, removing the product formed by the loading operation from the thus withdrawn solution and returning the resulting liquor to the group of columns being loaded, passing the other solution of ionogenic substance through the second group of columns to be regenerated and withdrawing the product formed in this regenerating operation from the last column in this second group of columns, disconnecting the first column in the group of columns being regenerated and connecting same as the last column in the group of columns being loaded, disconnecting the first column in the group of columns being loaded and connecting same as the last column in the group being regenerated and thereafter repeating the above described loading and regenerating operation through the new groups of columns; the improvements whereby a product substantially free of regenerating substance is obtained from the regenerating operation, said improvements comprising returning the liquor resulting from removal of the product formed during the loading operation to an intermediate column in the group of columns being loaded, disconnecting the first column in the group of columns being regenerated when said first column is only partially regenerated and connecting said partially regenerated column as the last column in the group of columns being loaded and, in repeating said loading and regenerating operations, returning the liquor resulting from removal of the product formed during the loading operation to the column adjacent, and subsequent, to the intermediate column being loaded and to which this liquor was previously returned.

2. The process of claim 1 wherein the loaded and regenerated columns are washed before being connected to the group of columns undergoing regeneration and loading, respectively.

3. The process of claim 1 wherein the product formed in the loading operation is removed by cooling the with- 7 drawn solution and crystallizing said product, and the resulting liquor is concentrated prior to. its return to the column being loaded.

4. The process of claim 1 wherein the product formed in the loading operation is recovered from the withdrawn solution by crystallization.

5. The process of claim 1 wherein said ion-exchanger is a cation-exchange resin, one of said solutions is an aqueous solution of an alkali metal salt and the other is an aqueous solution of an alkaline earth metal salt.

6. In effecting double conversion between an aqueous solution of KCl and an aqueous solution of Ca(NO3)2 by alternately contacting columns filled with a cation exchange resin first with said Ca(NOs)z solution to load said cation exchange resin with Ca ions and form KNOa solution and then with'the aqueous solution of KCl to regenerate said cation exchange resin with K ions and form CaClz solution using'a process involving the steps of providing a first group of columns connected together in series to be loaded and a second group of columns connected together in a series to be regenerated, passing the Ca(NO3)2 solution through the first group of columns to load the resin therein with Ca ions and withdrawing from the last column of this group of columns a solution containing KNO3 formed by the loading operation and Ca(NO3)2, removing the KNO: formed by the loading operation from the thus withdrawn solution and returning the resulting Ca(NOs)z-containing liquor to the group of columns being loaded, passing the solution of KCl through the second group of columns to be regenerated and withdrawing CaCla formed in this regenerating operation from the last column in this second group of columns, disconnecting the first column in the group of columns being regenerated and connecting same as the last column in the group of columns being loaded, disconnecting the first column in the group of columns being loaded and connecting same as the last column in the group being regenerated and thereafter repeating the above described loading and regenerating operation through the new groups of columns; the improvernents whereby a product substantially free of KCl is obtained from the regenerating operation, said improvements comprising returning the Ca(NOa)2-containing liquor resulting from removal of the KNO: formed during the loading operation to an intermediate column in the group of columns being loaded, disconnecting the first column in the group of columns being regenerated when said first column is only partially regenerated with K ions and connecting said partially regenerated column as the last column in the group of columns being loaded and, in repeating said loading and regenerating operations, returning the Ca(NO3)z-containing liquor resulting from removal of the KNO: formed during the loading operation to the column adjacent, and subsequent, to the intermediate column being loaded and to which this liquor was previously returned.

7. The process of claim 6 wherein the KNOa formed in the loading operation is recovered from the withdrawn solution by crystallization.

References Cited in the file of this patent UNITED STATES PATENTS 1,859,738 Johnson May 24, 1932 2,344,617 Johnsen Mar. 21, 1944 V FOREIGN PATENTS 415,660 Great Britain Aug. 30, 1934 

1. IN EFFECTING DOUBLE CONVERSION BETWEEN TWO SOLUTIONS OF IONOGENIC SUBSTANCES BY ALTERNATELY CONTACTING COLUMNS FILLED WITH ION EXCHANGER FIRST WITH ONE OF SAID SOLUTIONS TO LOAD THE ION EXCHANGER AND THEN WITH THE OTHER OF SAID SOLUTIONS TO REGENERATE AND THEN WITH THE USING A PROCESS INVOLVING THE STEPS OF PROVIDING A FIRST GROUP OF COLUMNS CONNECTED TOGETHER IN SERIES TO BE LOADED AND A SECOND GROUP OF COLUMNS CONNECTED TOGETHER IN SERIES TO BE REGENERATED, PASSING THE LOADING SOLUTION THROUGH THE FIRST GROUP OF COLUMNS TO LOAD THE ION EXCHANGER THEREIN AND WITHDRAWING FROM THE LAST COLUMN OF THIS GROUP OF COLUMNS A SOLUTION CONTAINING THE PRODUCT FORMED BY THE LOADING OPERATION AND THE IONOGENIC SUBSTANCE OF THE LOADING SOLUTION, REMOVING THE PRODUCT FORMED BY THE LOADING OPERATION FROM THE THUS WITHDRAWN SOLUTION AND RETURNING THE RESULTING LIQUOR TO THE GROUP OF COLUMNS BEING LOADED, PASSING THE OTHER SOLUTION OF IONOGENIC SUBSTANCE THROUGH THE SECOND GROUP OF COLUMNS TO BE REGENERATED AND WITHDRAWING THE PRODUCT FORMED IN THIS REGENERATING OPERATION FROM THE LAST COLUMN IN THIS SECOND GROUP OF COLUMNS, DISCONNECTING THE FIRST COLUMN IN THE GROUP OF COLUMNS BEING REGENERATED AND CONNECTING SAME AS THE LAST COLUMN IN THE PRODUCT OF COLUMNS BEING LOADED, DISCONNECTING THE FIRST COLUMN IN THE GROUP OF COLUMNS BEING LOADED AND CONNECTING SAME AS THE LAST COLUMN IN THE GROUP BEING REGENERATED AND THEREAFTER REPEATING THE ABOVE DESCRIBED LOADING AND REGENERATING OPERATION THROUGH THE NEW GROUPS OF COLUMNS; THE IMPROVEMENTS WHEREBY A PRODUCT SUBSTANTIALLY FREE OF REGENERATING SUBSTANCE IS OBTAINED FROM THE REGENERATING OPERATION, SAID IMPROVEMENTS COMPRISING RETURNING THE LIQUOR RESULTING FROM REMOVAL OF THE PRODUCT FORMED DURING THE LOADING OPERATION TO AN INTERMEDIATE COLUMN IN THE GROUP OF COLUMNS BEING LOADED, DISCONNECTING THE FIRST COLUMN IN THE GROUP OF COLUMNS BEING REGENERATED WHEN SAID FIRST COLUMN IS ONLY PARTIALLY REGENERATED AND CONNECTING SAID PARTIALLY REGENERATED COLUMN AS THE LAST COLUMN IN THE GROUP OF COLUMNS BEING LOADED AND, IN REPEATING SAID LOADING AND REGENERATING OPERATIONS, RETURNING THE LIQUOR RESULTING FROM REMOVAL OF THE PRODUCT FORMED DURING THE LOADING OPERATION TO THE COLUMN ADJACENT, AND SUBSEQUENT, TO THE INTERMEDIATE COLUMN BEING LOADED AND TO WHICH THIS LIQUOR WAS PREVIOUSLY RETURNED. 